RFC 1867 - Form-based File Upload in HTML

JSP Tutorials - Herong's Tutorial Examples

∟RFC 1867 - Form-based File Upload in HTML

This section describes the file upload specification, 'RFC 1867 - Form-based File Upload in HTML', proposed by E. Nebel and L. Masinter in 1995.

To set up a Web page for users to upload files, you need to:

Understand how file upload works - read the file upload specification: "RFC 1867 - Form-based File Upload in HTML".
A Web page with special HTML tags to instruct the browser to include a file in the HTTP request.
A Web server handler program to handle the HTTP request that contains the uploaded file.

Let's look at the specification first. In order to upload files to Web servers, RFC 1867 - Form-based File Upload in HTML was proposed by E. Nebel and L. Masinter in 1995. It offers:

1. A new type code, FILE, for the INPUT HTML tag:

   <INPUT TYPE="FILE" NAME="field_name" VALUE="file_name">

A Web browser should interpret this tag as an input field to enter a file name on the local system. Some browsers, like Internet Explorer, will also display button called "Browse" next to this field to allow users to browse the local file system to select a file name.

2. A new encryption type code, multipart/form-date, for the FORM HTML tag:

   <FORM ACTION="url" METHOD="post" ENCTYPE="multipart/form-data">

When a user clicks the submit button on Web form with this tag, the Web browser should collect data from all input fields and submit to the specified URL. The browser should also follow the following rules:

If "get" is specified as the method, data will be submitted as part of the GET header line of the HTTP request.
If "post" is specified as the method, data will be submitted as the body of the HTTP request.
If "application/x-www-form-urlencoded" is specified as the encryption type, names and values of all input fields will be encoded together based on the URL encoding specification.
If no encryption type is specified, "application/x-www-form-urlencoded" will be used as the default encryption type.
If "multipart/form-data" is specified as the encryption type, data will be submitted in multiple parts with one part for one input field. Parts are separated by a boundary identification string, which should be given as the "boundary" attribute of the "Content-type" header line if the HTTP request.
If "application/x-www-form-urlencoded" is specified as the encryption type, only the file name of a FILE type input field will be submitted as the value of the field. The content of the file will not be submitted.
If "multipart/form-data" is specified as the encryption type, only the file name of a FILE type input field will be submitted as the value of the field. The content of the file will not be submitted.

When "multipart/form-data" is specified as the encryption type, the format of the HTTP request body should look like this:

--boundary_identification_string
input_part_1
--boundary_identification_string
input_part_2
--boundary_identification_string
input_part_3
......
--boundary_identification_string--

The format of each input part is depending on the input field type. For any types other than FILE, the format should look like this:

Content-Disposition: form-data; name="field_name"

field_value

For an input field of type FILE, the format of the input part should look like this:

Content-Disposition: form-data; name="field_name"; filename="file_name"
Content-Type: file_type

file_content

Here is sample HTML page to show you how to use FILE input field and "multipart/form-data" encryption type:

<?xml version="1.0"?>
<html><body>
<!-- UploadSample.html
     Copyright (c) 2004 by Dr. Herong Yang
-->
<form action="some_url" enctype="multipart/form-data" method="post">
<input type="text" name="author" value="Herong Yang"/>
<input type="file" name="picture" value="C:\dot.gif"/>
<input type="submit" name="submit" value="Submit"/>
</form>
</body></html>

The browser should submit the following multiple-part HTTP request body when users click the submit button:

--boundary_identification_string
Content-Disposition: form-data; name="author"

Herong Yang
--boundary_identification_string
Content-Disposition: form-data; name="picture"; filename="C:\dot.gif"
Content-Type: image/gif

dot.gif_file_content
--boundary_identification_string
Content-Disposition: form-data; name="submit"

Submit
--boundary_identification_string--

Last update: 2012.

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JSP (JavaServer Pages) Overview

Tomcat 7 Installation on Windows Systems

JSP Scripting Elements

Java Servlet Introduction

JSP Implicit Objects

Syntax of JSP Pages and JSP Documents

JSP Application Session

Managing Cookies in JSP Pages

JavaBean Objects and "useBean" Action Elements